/*
 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

 /**
  * @file
  * bitstream reader API header.
  */

#ifndef AVCODEC_GET_BITS_H
#define AVCODEC_GET_BITS_H

#include <stdint.h>

#if defined(__cplusplus) &&  __cplusplus < 201703L
   #define REGISTER       register
#else
    #define REGISTER      
#endif

static const uint8_t ff_golomb_vlc_len[512] = {
	19,17,15,15,13,13,13,13,11,11,11,11,11,11,11,11,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
	7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
	5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
	5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
	3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
	3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
	3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
	3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
};


static const uint8_t ff_ue_golomb_vlc_code[512] = {
	32,32,32,32,32,32,32,32,31,32,32,32,32,32,32,32,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,
	7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9,10,10,10,10,11,11,11,11,12,12,12,12,13,13,13,13,14,14,14,14,
	3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
	5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
	2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

static const int8_t ff_se_golomb_vlc_code[512] = {
	17, 17, 17, 17, 17, 17, 17, 17, 16, 17, 17, 17, 17, 17, 17, 17,  8, -8,  9, -9, 10,-10, 11,-11, 12,-12, 13,-13, 14,-14, 15,-15,
	4,  4,  4,  4, -4, -4, -4, -4,  5,  5,  5,  5, -5, -5, -5, -5,  6,  6,  6,  6, -6, -6, -6, -6,  7,  7,  7,  7, -7, -7, -7, -7,
	2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
	3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3, -3, -3, -3, -3, -3, -3, -3, -3, -3, -3, -3, -3, -3, -3, -3, -3,
	1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
	1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
	0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
	0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
	0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
	0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
	0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
	0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
	0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
};


/*
 * Safe bitstream reading:
 * optionally, the get_bits API can check to ensure that we
 * don't read past input buffer boundaries. This is protected
 * with CONFIG_SAFE_BITSTREAM_READER at the global level, and
 * then below that with UNCHECKED_BITSTREAM_READER at the per-
 * decoder level. This means that decoders that check internally
 * can "#define UNCHECKED_BITSTREAM_READER 1" to disable
 * overread checks.
 * Boundary checking causes a minor performance penalty so for
 * applications that won't want/need this, it can be disabled
 * globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
 */

typedef struct GetBitContext {
	const uint8_t *buffer, *buffer_end;
	int index;
	int size_in_bits;
	int size_in_bits_plus8;
} GetBitContext;

/* Bitstream reader API docs:
 * name
 *   arbitrary name which is used as prefix for the internal variables
 *
 * gb
 *   getbitcontext
 *
 * OPEN_READER(name, gb)
 *   load gb into local variables
 *
 * CLOSE_READER(name, gb)
 *   store local vars in gb
 *
 * UPDATE_CACHE(name, gb)
 *   Refill the internal cache from the bitstream.
 *   After this call at least MIN_CACHE_BITS will be available.
 *
 * GET_CACHE(name, gb)
 *   Will output the contents of the internal cache,
 *   next bit is MSB of 32 or 64 bits (FIXME 64 bits).
 *
 * SHOW_UBITS(name, gb, num)
 *   Will return the next num bits.
 *
 * SHOW_SBITS(name, gb, num)
 *   Will return the next num bits and do sign extension.
 *
 * SKIP_BITS(name, gb, num)
 *   Will skip over the next num bits.
 *   Note, this is equivalent to SKIP_CACHE; SKIP_COUNTER.
 *
 * SKIP_CACHE(name, gb, num)
 *   Will remove the next num bits from the cache (note SKIP_COUNTER
 *   MUST be called before UPDATE_CACHE / CLOSE_READER).
 *
 * SKIP_COUNTER(name, gb, num)
 *   Will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS).
 *
 * LAST_SKIP_BITS(name, gb, num)
 *   Like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER.
 *
 * BITS_LEFT(name, gb)
 *   Return the number of bits left
 *
 * For examples see get_bits, show_bits, skip_bits, get_vlc.
 */

#ifdef LONG_BITSTREAM_READER
#   define MIN_CACHE_BITS 32
#else
#   define MIN_CACHE_BITS 25
#endif

#define OPEN_READER_NOSIZE(name, gb)            \
    unsigned int name ## _index = (gb)->index;  \
    unsigned int av_unused name ## _cache

#if UNCHECKED_BITSTREAM_READER
#define OPEN_READER(name, gb) OPEN_READER_NOSIZE(name, gb)

#define BITS_AVAILABLE(name, gb) 1
#else
#define OPEN_READER(name, gb)                   \
    OPEN_READER_NOSIZE(name, gb);               \
    unsigned int name ## _size_plus8 = (gb)->size_in_bits_plus8

#define BITS_AVAILABLE(name, gb) name ## _index < name ## _size_plus8
#endif

#define CLOSE_READER(name, gb) (gb)->index = name ## _index

# ifdef LONG_BITSTREAM_READER

# define UPDATE_CACHE_LE(name, gb) name ## _cache = \
      AV_RL64((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)

# define UPDATE_CACHE_BE(name, gb) name ## _cache = \
      AV_RB64((gb)->buffer + (name ## _index >> 3)) >> (32 - (name ## _index & 7))

#else

# define UPDATE_CACHE_LE(name, gb) name ## _cache = \
      AV_RL32((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)

# define UPDATE_CACHE_BE(name, gb) name ## _cache = \
      AV_RB32((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7)

#endif


#ifdef BITSTREAM_READER_LE

# define UPDATE_CACHE(name, gb) UPDATE_CACHE_LE(name, gb)

# define SKIP_CACHE(name, gb, num) name ## _cache >>= (num)

#else

# define UPDATE_CACHE(name, gb) UPDATE_CACHE_BE(name, gb)

# define SKIP_CACHE(name, gb, num) name ## _cache <<= (num)

#endif

#ifndef NEG_USR32
#define NEG_USR32(a,s) (((uint32_t)(a))>>(32-(s)))
#endif

#ifndef NEG_SSR32
#   define NEG_SSR32(a,s) ((( int32_t)(a))>>(32-(s)))
#endif

#ifndef sign_extend
static inline av_const int sign_extend(int val, unsigned bits)
{
	unsigned shift = 8 * sizeof(int) - bits;
	union { unsigned u; int s; } v = { (unsigned)val << shift };
	return v.s >> shift;
}
#endif

#ifndef zero_extend
static inline av_const unsigned zero_extend(unsigned val, unsigned bits)
{
	return (val << ((8 * sizeof(int)) - bits)) >> ((8 * sizeof(int)) - bits);
}
#endif


#if UNCHECKED_BITSTREAM_READER
#   define SKIP_COUNTER(name, gb, num) name ## _index += (num)
#else
#   define SKIP_COUNTER(name, gb, num) \
    name ## _index = FFMIN(name ## _size_plus8, name ## _index + (num))
#endif

#define BITS_LEFT(name, gb) ((int)((gb)->size_in_bits - name ## _index))

#define SKIP_BITS(name, gb, num)                \
    do {                                        \
        SKIP_CACHE(name, gb, num);              \
        SKIP_COUNTER(name, gb, num);            \
    } while (0)

#define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)

#define SHOW_UBITS_LE(name, gb, num) zero_extend(name ## _cache, num)
#define SHOW_SBITS_LE(name, gb, num) sign_extend(name ## _cache, num)

#define SHOW_UBITS_BE(name, gb, num) NEG_USR32(name ## _cache, num)
#define SHOW_SBITS_BE(name, gb, num) NEG_SSR32(name ## _cache, num)

#ifdef BITSTREAM_READER_LE
#   define SHOW_UBITS(name, gb, num) SHOW_UBITS_LE(name, gb, num)
#   define SHOW_SBITS(name, gb, num) SHOW_SBITS_LE(name, gb, num)
#else
#   define SHOW_UBITS(name, gb, num) SHOW_UBITS_BE(name, gb, num)
#   define SHOW_SBITS(name, gb, num) SHOW_SBITS_BE(name, gb, num)
#endif

#define GET_CACHE(name, gb) ((uint32_t) name ## _cache)

static inline int get_bits_count(const GetBitContext *s)
{
	return s->index;
}

/**
 * Skips the specified number of bits.
 * @param n the number of bits to skip,
 *          For the UNCHECKED_BITSTREAM_READER this must not cause the distance
 *          from the start to overflow int32_t. Staying within the bitstream + padding
 *          is sufficient, too.
 */
static inline void skip_bits_long(GetBitContext *s, int n)
{
#if UNCHECKED_BITSTREAM_READER
	s->index += n;
#else
	s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
#endif
}

/**
 * Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
 * if MSB not set it is negative
 * @param n length in bits
 */
static inline int get_xbits(GetBitContext *s, int n)
{
    REGISTER int sign;
    REGISTER int32_t cache;
	OPEN_READER(re, s);
	av_assert2(n > 0 && n <= 25);
	UPDATE_CACHE(re, s);
	cache = GET_CACHE(re, s);
	sign = ~cache >> 31;
	LAST_SKIP_BITS(re, s, n);
	CLOSE_READER(re, s);
	return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
}

static inline int get_xbits_le(GetBitContext *s, int n)
{
    REGISTER int sign;
    REGISTER int32_t cache;
	OPEN_READER(re, s);
	av_assert2(n > 0 && n <= 25);
	UPDATE_CACHE_LE(re, s);
	cache = GET_CACHE(re, s);
	sign = sign_extend(~cache, n) >> 31;
	LAST_SKIP_BITS(re, s, n);
	CLOSE_READER(re, s);
	return (zero_extend(sign ^ cache, n) ^ sign) - sign;
}

static inline int get_sbits(GetBitContext *s, int n)
{
    REGISTER int tmp;
	OPEN_READER(re, s);
	av_assert2(n > 0 && n <= 25);
	UPDATE_CACHE(re, s);
	tmp = SHOW_SBITS(re, s, n);
	LAST_SKIP_BITS(re, s, n);
	CLOSE_READER(re, s);
	return tmp;
}

/**
 * Read 1-25 bits.
 */
static inline unsigned int get_bits(GetBitContext *s, int n)
{
    REGISTER int tmp;
	OPEN_READER(re, s);
	av_assert2(n > 0 && n <= 25);
	UPDATE_CACHE(re, s);
	tmp = SHOW_UBITS(re, s, n);
	LAST_SKIP_BITS(re, s, n);
	CLOSE_READER(re, s);
	return tmp;
}

/**
 * Read 0-25 bits.
 */
static av_always_inline int get_bitsz(GetBitContext *s, int n)
{
	return n ? get_bits(s, n) : 0;
}

static inline unsigned int get_bits_le(GetBitContext *s, int n)
{
    REGISTER int tmp;
	OPEN_READER(re, s);
	av_assert2(n > 0 && n <= 25);
	UPDATE_CACHE_LE(re, s);
	tmp = SHOW_UBITS_LE(re, s, n);
	LAST_SKIP_BITS(re, s, n);
	CLOSE_READER(re, s);
	return tmp;
}

/**
 * Show 1-25 bits.
 */
static inline unsigned int show_bits(GetBitContext *s, int n)
{
    REGISTER int tmp;
	OPEN_READER_NOSIZE(re, s);
	av_assert2(n > 0 && n <= 25);
	UPDATE_CACHE(re, s);
	tmp = SHOW_UBITS(re, s, n);
	return tmp;
}

static inline void skip_bits(GetBitContext *s, int n)
{
	OPEN_READER(re, s);
	LAST_SKIP_BITS(re, s, n);
	CLOSE_READER(re, s);
}

static inline unsigned int get_bits1(GetBitContext *s)
{
	unsigned int index = s->index;
	uint8_t result = s->buffer[index >> 3];
#ifdef BITSTREAM_READER_LE
	result >>= index & 7;
	result &= 1;
#else
	result <<= index & 7;
	result >>= 8 - 1;
#endif
#if !UNCHECKED_BITSTREAM_READER
	if (s->index < s->size_in_bits_plus8)
#endif
		index++;
	s->index = index;

	return result;
}

static inline unsigned int show_bits1(GetBitContext *s)
{
	return show_bits(s, 1);
}

static inline void skip_bits1(GetBitContext *s)
{
	skip_bits(s, 1);
}

/**
 * Read 0-32 bits.
 */
static inline unsigned int get_bits_long(GetBitContext *s, int n)
{
	av_assert2(n >= 0 && n <= 32);
	if (!n) {
		return 0;
	}
	else if (n <= MIN_CACHE_BITS) {
		return get_bits(s, n);
	}
	else {
#ifdef BITSTREAM_READER_LE
		unsigned ret = get_bits(s, 16);
		return ret | (get_bits(s, n - 16) << 16);
#else
		unsigned ret = get_bits(s, 16) << (n - 16);
		return ret | get_bits(s, n - 16);
#endif
	}
}

/**
 * Read 0-64 bits.
 */
static inline uint64_t get_bits64(GetBitContext *s, int n)
{
	if (n <= 32) {
		return get_bits_long(s, n);
	}
	else {
#ifdef BITSTREAM_READER_LE
		uint64_t ret = get_bits_long(s, 32);
		return ret | (uint64_t)get_bits_long(s, n - 32) << 32;
#else
		uint64_t ret = (uint64_t)get_bits_long(s, n - 32) << 32;
		return ret | get_bits_long(s, 32);
#endif
	}
}

/**
 * Read 0-32 bits as a signed integer.
 */
static inline int get_sbits_long(GetBitContext *s, int n)
{
	// sign_extend(x, 0) is undefined
	if (!n)
		return 0;

	return sign_extend(get_bits_long(s, n), n);
}

/**
 * Show 0-32 bits.
 */
static inline unsigned int show_bits_long(GetBitContext *s, int n)
{
	if (n <= MIN_CACHE_BITS) {
		return show_bits(s, n);
	}
	else {
		GetBitContext gb = *s;
		return get_bits_long(&gb, n);
	}
}

static inline int check_marker(void *logctx, GetBitContext *s, const char *msg)
{
	int bit = get_bits1(s);
	if (!bit)
		av_log(logctx, AV_LOG_INFO, "Marker bit missing at %d of %d %s\n",
			get_bits_count(s) - 1, s->size_in_bits, msg);

	return bit;
}

/**
 * Initialize GetBitContext.
 * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
 *        larger than the actual read bits because some optimized bitstream
 *        readers read 32 or 64 bit at once and could read over the end
 * @param bit_size the size of the buffer in bits
 * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
 */
static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
	int bit_size)
{
	int buffer_size;
	int ret = 0;

	if (bit_size >= INT_MAX - FFMAX(7, AV_INPUT_BUFFER_PADDING_SIZE * 8) || bit_size < 0 || !buffer) {
		bit_size = 0;
		buffer = NULL;
		ret = AVERROR_INVALIDDATA;
	}

	buffer_size = (bit_size + 7) >> 3;

	s->buffer = buffer;
	s->size_in_bits = bit_size;
	s->size_in_bits_plus8 = bit_size + 8;
	s->buffer_end = buffer + buffer_size;
	s->index = 0;

	return ret;
}

/**
 * Initialize GetBitContext.
 * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
 *        larger than the actual read bits because some optimized bitstream
 *        readers read 32 or 64 bit at once and could read over the end
 * @param byte_size the size of the buffer in bytes
 * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
 */
static inline int init_get_bits8(GetBitContext *s, const uint8_t *buffer,
	int byte_size)
{
	if (byte_size > INT_MAX / 8 || byte_size < 0)
		byte_size = -1;
	return init_get_bits(s, buffer, byte_size * 8);
}

static inline const uint8_t *align_get_bits(GetBitContext *s)
{
	int n = -get_bits_count(s) & 7;
	if (n)
		skip_bits(s, n);
	return s->buffer + (s->index >> 3);
}

static inline unsigned get_ue_golomb_long(GetBitContext *gb)
{
	unsigned buf, log;

	buf = show_bits_long(gb, 32);
	log = 31 - av_log2(buf);
	skip_bits_long(gb, log);

	return get_bits_long(gb, log + 1) - 1;
}

static inline int get_se_golomb(GetBitContext *gb)
{
	unsigned int buf;
	OPEN_READER(re, gb);
	UPDATE_CACHE(re, gb);
	buf = GET_CACHE(re, gb);

	if (buf >= (1 << 27))
	{
		buf >>= 32 - 9;
		LAST_SKIP_BITS(re, gb, ff_golomb_vlc_len[buf]);
		CLOSE_READER(re, gb);

		return ff_se_golomb_vlc_code[buf];
	}
	else
	{
		int log = av_log2(buf), sign;
		LAST_SKIP_BITS(re, gb, 31 - log);
		UPDATE_CACHE(re, gb);
		buf = GET_CACHE(re, gb);

		buf >>= log;

		LAST_SKIP_BITS(re, gb, 32 - log);
		CLOSE_READER(re, gb);

		sign = (buf & 1);
		sign = -sign;
		buf = ((buf >> 1) ^ sign) - sign;

		return buf;
	}
}

static inline int get_ue_golomb(GetBitContext *gb)
{
	unsigned int buf;
	OPEN_READER(re, gb);
	UPDATE_CACHE(re, gb);
	buf = GET_CACHE(re, gb);
	if (buf >= (1 << 27))
	{
		buf >>= 32 - 9;
		LAST_SKIP_BITS(re, gb, ff_golomb_vlc_len[buf]);
		CLOSE_READER(re, gb);
		return ff_ue_golomb_vlc_code[buf];
	}
	else
	{
		int log = 2 * av_log2(buf) - 31;
		LAST_SKIP_BITS(re, gb, 32 - log);
		CLOSE_READER(re, gb);
		if (log < 7)
			return AVERROR_INVALIDDATA;
		buf >>= log;
		buf--;
		return buf;
	}
}


static inline int get_se_golomb_long(GetBitContext *gb)
{
	unsigned int buf = get_ue_golomb_long(gb);
	int sign = (buf & 1) - 1;
	return ((buf >> 1) ^ sign) + 1;
}

static inline int get_ue_golomb_31(GetBitContext *gb)
{
	unsigned int buf;
	OPEN_READER(re, gb);
	UPDATE_CACHE(re, gb);
	buf = GET_CACHE(re, gb);

	buf >>= 32 - 9;
	LAST_SKIP_BITS(re, gb, ff_golomb_vlc_len[buf]);
	CLOSE_READER(re, gb);
	return ff_ue_golomb_vlc_code[buf];
}
/**
 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
 * If the vlc code is invalid and max_depth>1, then the number of bits removed
 * is undefined.
 */
#define GET_VLC(code, name, gb, table, bits, max_depth)         \
    do {                                                        \
        int n, nb_bits;                                         \
        unsigned int index;                                     \
                                                                \
        index = SHOW_UBITS(name, gb, bits);                     \
        code  = table[index][0];                                \
        n     = table[index][1];                                \
                                                                \
        if (max_depth > 1 && n < 0) {                           \
            LAST_SKIP_BITS(name, gb, bits);                     \
            UPDATE_CACHE(name, gb);                             \
                                                                \
            nb_bits = -n;                                       \
                                                                \
            index = SHOW_UBITS(name, gb, nb_bits) + code;       \
            code  = table[index][0];                            \
            n     = table[index][1];                            \
            if (max_depth > 2 && n < 0) {                       \
                LAST_SKIP_BITS(name, gb, nb_bits);              \
                UPDATE_CACHE(name, gb);                         \
                                                                \
                nb_bits = -n;                                   \
                                                                \
                index = SHOW_UBITS(name, gb, nb_bits) + code;   \
                code  = table[index][0];                        \
                n     = table[index][1];                        \
            }                                                   \
        }                                                       \
        SKIP_BITS(name, gb, n);                                 \
    } while (0)

#define GET_RL_VLC(level, run, name, gb, table, bits,  \
                   max_depth, need_update)                      \
    do {                                                        \
        int n, nb_bits;                                         \
        unsigned int index;                                     \
                                                                \
        index = SHOW_UBITS(name, gb, bits);                     \
        level = table[index].level;                             \
        n     = table[index].len;                               \
                                                                \
        if (max_depth > 1 && n < 0) {                           \
            SKIP_BITS(name, gb, bits);                          \
            if (need_update) {                                  \
                UPDATE_CACHE(name, gb);                         \
            }                                                   \
                                                                \
            nb_bits = -n;                                       \
                                                                \
            index = SHOW_UBITS(name, gb, nb_bits) + level;      \
            level = table[index].level;                         \
            n     = table[index].len;                           \
            if (max_depth > 2 && n < 0) {                       \
                LAST_SKIP_BITS(name, gb, nb_bits);              \
                if (need_update) {                              \
                    UPDATE_CACHE(name, gb);                     \
                }                                               \
                nb_bits = -n;                                   \
                                                                \
                index = SHOW_UBITS(name, gb, nb_bits) + level;  \
                level = table[index].level;                     \
                n     = table[index].len;                       \
            }                                                   \
        }                                                       \
        run = table[index].run;                                 \
        SKIP_BITS(name, gb, n);                                 \
    } while (0)

static inline int decode012(GetBitContext *gb)
{
	int n;
	n = get_bits1(gb);
	if (n == 0)
		return 0;
	else
		return get_bits1(gb) + 1;
}

static inline int decode210(GetBitContext *gb)
{
	if (get_bits1(gb))
		return 0;
	else
		return 2 - get_bits1(gb);
}

static inline int get_bits_left(GetBitContext *gb)
{
	return gb->size_in_bits - get_bits_count(gb);
}

static inline int skip_1stop_8data_bits(GetBitContext *gb)
{
	if (get_bits_left(gb) <= 0)
		return AVERROR_INVALIDDATA;

	while (get_bits1(gb)) {
		skip_bits(gb, 8);
		if (get_bits_left(gb) <= 0)
			return AVERROR_INVALIDDATA;
	}

	return 0;
}

#endif /* AVCODEC_GET_BITS_H */
